The present invention relates to paving machines, and more particularly to paving screed assemblies for paving machines.
Screed assemblies used with paving machines to level paving material, typically asphalt, applied by the machine onto a generally horizontal base surface, such as a road bed, are well known. A screed assembly often includes both a main screed and one or more screed extensions connected with the main screed. The screed extension may either be fixedly attached (e.g., bolted) to a lateral end of the main screed (or an outer end of another screed extension) or movably attached to the main screed.
In general, a typical screed assembly levels the paving material into a mat having the general form of an elongated strip. When it is desired to pave a mat of material having a width that exceeds the maximum width of the screed assembly, the paving machine must typically pave two or more parallel mat strips to achieve the desired overall mat width. Each of these mat strips has a longitudinally-extending side edge that must either abut or overlap the proximal edge of the adjacent mat strip so that a continuous surface is formed across the overall width of the mat of material. It is preferred to closely abut the edges of the adjacent mat strips such that, after a subsequent compacting or rolling operation, an integral zone of paving material, referred to as a "joint", exists at the intersection of the adjacent mat strips.
However, if the subsequently paved or "second" mat strip is not carefully applied, one of two adverse conditions may be created at the intersection of the adjacent mat strips. If the second mat strip overlaps the other or "first" strip by a more than certain distance, an upraised section or bump is created at the joint, which may not be eliminated by a subsequent rolling operation. If the second mat strip is applied such that the proximal edges of the first and second mat strips are spaced apart by more than a minimal distance, a gap is created between the mat strips that cannot be eliminated by a rolling operation. In this situation, a subsequent operation to fill the gap with paving material is necessary, creating a weakened zone in the mat of material. Typically, this weakened zone of a material mat will be the first section of the mat that fails (i.e., cracks or crumbles) after a period of use.
In order to eliminate the occurrence of the adverse mat conditions described above, it is known to form a downward step at the edge of the first mat strip and then to pave the second mat strip such that the proximal edge of the second strip overlaps this stepped edge. The joint formed by this procedure is relatively strong and level. Devices for forming the edges of a mat strip to create stepped edges are known. These devices typically have a frame that attaches to a screed assembly and an edge-forming plate connected to the frame. The forming plate is located vertically lower than the screed plate(s) of the screed assembly and may be also be angled so as to create a downwardly-tapered step. However, these known devices generally have minimal or no capability to adjust the vertical height, taper angle and/or angle of attack of the forming plate with respect to the screed plates of the main screed assembly.
It is therefore desirable to provide a device for an edge-forming device for a screed assembly that has a fully adjustable edge-forming plate. Further, it is also desirable to provide such a device that is capable of being connected with existing screed assemblies without the need for any substantial modifications to the existing screed assemblies.